(1) Field of the Invention:
The present invention relates to a filter plate opening mechanism for successively opening a plurality of filter plates at substantially equal intervals for filter presses.
(2) Description of the Prior Art:
Heretofore, various kinds of filter plate shifters or filter plate opening mechanisms have been suggested. For example, each two adjacent filter plates of a filter press are connected to each other by means of a chain 2 of a determined length, as illustrated in FIG. 1, so that after completion of dewatering or squeeze of slurry, movement of one of the plates in an opening direction by means of a moving ratchet causes to move the other of the plates connected by the chain to the one of the plates until the moving ratchet is stopped by an abutment thereof against a movable head or a filter plate to the side of the movable head side. At the moment the moving stops, an overload detecting device provided in a driving device stops a motor for driving the moving ratchet. Under the opened condition, the filter cakes are discharged or removed from the opened filter chambers. Then the moving ratchet is driven in the reverse direction until it is stopped by its abutment against a filter plate to the side of a front head frame. By repeating these operations the plurality of the filter plates are partially opened in succession.
Such a shifter or filter plate opening mechanism is substantially effective for filter presses having only a small number of filter plates. With filter plates having an large number of filter plates, however, opening distances between the adjacent filter plates are markedly different at the initial and last stages of the opening owing to the elastic restoration of packing materials or filter cloths of the already opened filter plates. Such a variation in opening distance of the filter plates may obstruct the discharge of filter cakes by vibrating filter cloths by means of rotating vibrating devices and the filter cloth washing operation by insertion of a washing device between the filter cloths.
To overcome this problem, it has also been suggested to connect all the filter plates by chains of a constant length and to pull every other filter plates in an opening direction by means of a moving ratchet, such that the other filter plate than filter plate in intermediate positions is slightly shifted or opened to an excess extent in consideration of the elastic restoration of the packing materials and filter cloths. In this case, when the moving ratchet moves in the reverse direction in the preparation for opening the next filter plates, the movement of the ratchet causes to return in the reverse direction the tail end filter plate, which is slightly opened, until the tail end filter plate strikes a closed or unopened filter plate because the moving ratchet never stops until it strikes the closed filter plate. Accordingly, the other filter plates which have already been opened are also returned by the chains to obstruct the discharge of filter cakes and particularly the filter cloth washing by the insertion of cleaning nozzles between the filter plates.